1. Field of the Invention
The present invention relates to a caulking roller and a sintered flanged pulley caulked by the caulking roller. Caulking is the operation in which two parts are joined tightly together to prevent leakage or slippage, in the present case by mating the two parts in the joint and upsetting the material of at least one of the two parts to interlock the parts and make them tight against one another.
2. Description of the Related Art
In a timing drive of a vehicular engine are used various pulleys on which a toothed belt is entrained, such as a cam pulley, a crank pulley, and an oil pump pulley. In each of these pulleys, annular flanges for keeping the position of the toothed belt and for preventing disengagement of the same belt are formed on both sides of a pulley body. However, the pulleys each having such annular flanges on both sides of its body are difficult to be formed integrally by sintering. According to the conventional method for fabricating sintered pulleys with annular flanges on both sides of their bodies, first a pulley body having a flange portion on one side is formed integrally by sintering, and then an annular flange formed using a separate material is caulked or tightly joined to the sintered pulley body.
FIGS. 4 and 5 illustrate a sintered, flanged cam pulley 1 as an example of a pulley to be used in a timing drive of a vehicular engine, of which FIG. 4 is a sectional view showing a state before caulking an annular flange 3 to a sintered cam pulley body 2 and FIG. 5 is a sectional view showing a caulked state of the annular flange 3 to the pulley body 2.
As shown in FIG. 4, teeth 2a are integrally formed on an outer periphery of the sintered cam pulley body 2, a flange portion 2b is integrally formed on an outer periphery of one end of the pulley body 2, and an axial bore 2c with key way is formed in a boss portion of the pulley body . Further, at the opposite end of the pulley body 2, i.e., on the side opposite to the integral flange portion 2b, there is formed an axial annular projection 2d. On an outer periphery side of the annular projection 2d is formed a stepped portion 2e. The tip of the annular projection 2d constitutes an allowance for caulking. The annular flange 3 is formed in a thin disc shape using a cold rolled steel sheet (e.g., SPCC) or a carbon steel (e.g., S35C).
The annular flange 3 is caulked to the sintered cam pulley body 2 in the following manner. An inner peripheral surface 3a of the annular flange 3 is fitted on the stepped portion 2e of the sintered cam pulley body 2 and then the tip of the annular projection 2d of the pulley body 2 is caulked by a caulking roller 9 which upsets the material of the projection to tightly join the flange 3 to the body 2.
FIGS. 6 and 7 illustrate a main portion of a caulking equipment 4 using rollers for caulking the sintered, flanged cam pulley 1 shown in FIGS. 4 and 5. FIG. 6 is a sectional showing a state before caulking in which the sintered, flanged cam pulley 1 is loaded into the caulking equipment 4, and FIG. 7 is a sectional view showing a state in which the sintered, flanged cam pulley loaded into the caulking equipment is being caulked.
As shown in FIGS. 6 and 7, the caulking equipment 4 using rollers are provided with a caulking head 5 and a jig 6, the caulking head 5 being threadedly connected with a lower end portion of a cylinder 7. Three to five caulking rollers 9 (two being shown in FIGS. 6 and 7) are mounted to a lower portion of the caulking head 5 at equal intervals in the circumferential direction, the caulking rollers 9 being supported rotatably on a roller support shaft 8 which extends in a direction perpendicular to the axis of the cylinder 7. The jig 6, which supports the sintered cam pulley body 2, is provided with a protrusion 6a at a position aligned with the axis of the cylinder 7.
FIG. 8 is a sectional view of the conventional caulking roller 9 used in the caulking equipment 4 shown in FIGS. 6 and 7.
FIGS. 9A and 9B are sectional views for explaining how to caulk the sintered, flanged cam pulley 1, using the conventional caulking roller 9 shown in FIG. 8. FIG. 9A is a partially sectional view showing a positional relation between the caulking roller 9 before caulking and the sintered, flanged cam pulley 1, and FIG. 9B is a partially sectional view of the sintered, flanged cam pulley 1 in a completely caulked state by the caulking roller 9.
The following description is now provided about caulking the sintered, flanged cam pulley 1 by means of the caulking equipment 4 using rollers which is shown in FIGS. 6 and 7. First, the axial bore 2c with key way formed in the sintered cam pulley body 2 is fitted on the protrusion 6a of the jig 6 and then, using the key way, the pulley body 2 is set so as not to rotate with respect to the jig 6. Subsequently, the inner peripheral surface 3a of the annular flange 3 is fitted on the stepped portion 2e of the sintered cam pulley body 2. Next, with use of a drive unit (not shown), the caulking head 5 is brought down while allowing it to rotate about the axis of the cylinder 7. As a result, the caulking rollers 9 in the caulking equipment come into abutment against end faces of the annular projection 2d of the sintered cam pulley body 2. As the caulking head 5 is further brought down under rotation, the caulking rollers 9, while rolling, cause the tip of the annular projection 2d to be upset or deformed plastically. As a result of this plastic deformation of the tip of the annular projection 2d, an excess metal portion is formed on both inner and outer periphery sides of the annular projection to complete the caulking work. In this way the annular flange 3 is fixed to the sintered cam pulley body 2.
However, since the toughness of the sintered cam pulley body 2 is lower than that of carbon steel (S35C), if the amount of caulking is taken too large in an effort to obtain a high flange pressure output and a high flange loosening torque, there arises the problem that the caulked portion of the sintered cam pulley body 2 is separated or the problem that the annular projection 2d of the pulley body 2 is cracked. Moreover, if the amount of caulking is small, the flange pressure output is low, making it impossible to obtain a predetermined performance, or the annular flange 3 becomes loose and rotates. In the conventional caulking work, therefore, the caulking quantity control range is narrow and production control is very difficult for obtaining a satisfactory performance of the sintered, flanged cam pulley 1.
The term xe2x80x9cflange pressure outputxe2x80x9d as referred to herein represents a maximum load imposed axially on the sintered cam pulley body 2 corresponding to disengagement of the annular flange 3 from the pulley body. The term xe2x80x9cflange loosening torquexe2x80x9d represents a maximum torque imposed circumferentially on the annular flange 3 corresponding to loosening of the annular flange with respect to the sintered cam pulley body 2.
In caulking the annular flange to the sintered pulley body, other sintered flanged pulleys than the sintered, flanged cam pulley 1 described above also involve the same problems as above.
Accordingly, it is an object of the present invention to solve the above-mentioned problems of the prior art and provide a caulking roller capable of attaining a high flange pressure output and a high flange loosening torque and capable of widening the caulking quantity control range, as well as to provide a sintered flanged pulley caulked by such caulking roller.
For achieving the above-mentioned object, in the first aspect of the present invention there is provided a caulking roller for caulking an annular flange to a sintered pulley body, the caulking roller having a first conical surface of a first angle and a second conical surface of a second angle smaller than the first angle, the second conical surface being contiguous to the first conical surface, the first and second conical surfaces being formed on an outer peripheral surface of the caulking roller.
In the second aspect of the present invention there is provided a sintered flanged pulley comprising a sintered pulley body and an annular flange caulked to the sintered pulley body, the sintered pulley body having at an end portion thereof an axial annular projection and a stepped portion formed on an outer periphery side of the annular projection, wherein an inner peripheral surface of the annular flange is fitted on the stepped portion of the sintered pulley body, the tip of the annular projection is upset or deformed plastically from the inner periphery side of the annular projection to the outer periphery side thereof by a caulking roller, the caulking roller having a first conical surface of a first angle and a second conical surface of a second angle smaller than the first angle, the second conical surface being contiguous to the first conical surface, the first and second conical surfaces being formed on an outer peripheral surface of the caulking roller, and the annular flange is thereby caulked to the sintered pulley body.
The inner peripheral surface of the annular flange is fitted on the stepped portion of the sintered pulley body and then the caulking roller is brought down, with the result that the first conical surface of the caulking roller comes into abutment against an edge of the inner peripheral surface of the annular projection in the sintered pulley body. With this abutment, the caulking roller begins rolling. As the caulking roller is further brought down, the first conical surface of the caulking roller causes the tip of the annular projection to undergo a plastic deformation from the inner to the outer periphery side of the annular projection. With a further descent of the caulking roller, the second conical surface of the caulking roller causes the plastically deformed tip of the annular projection to undergo a further plastic deformation sideways of the annular flange, whereby the caulking work is completed without forming any excess metal portion on the inner periphery side of the projection. In this way the annular flange is fixed to the sintered pulley body effectively.